DETECTIVES have found a car belonging to a 28-year-old mum from Sydney, who hasn't been seen by anyone in more than four days.

They believe the white 2016 Toyota Corolla, which was found dumped in the Burwood just a short drive away from Qi Yu's home, could provide crucial clues in finding her.

The young mother was seen by friends four days ago at her shared house on Loch Street in Campsie on Friday evening, according to New South Wales Police

The last anybody heard from Ms Yu, was when she made contact with family in her native China at about 7.15pm on that very same evening. The next morning her friends found her room empty and reported her missing.

NSW Police have now issued another plea for the public to help, adding there are now "grave concerns for her welfare".

Ms Yu's friends and family say her disappearance is out of character and her mother arrived from China yesterday to assist with the search.

Homicide Squad detectives are now assisting with the investigation and they want to know if anybody saw the dumped car in the hours after Ms Yu was last seen.

"Anyone that saw her vehicle between the hours of 7pm on Friday (June 8) and 8.30pm on Saturday (June 9) is urged to come forward," a NSW Police spokesperson said.

Police describe the vehicle as a white 2016 model Toyota Corolla with NSW registration plates DLK-13P. It was found at Lindsay Street, Burwood.